.downloadbttn {
    position: absolute;
    left: 50%;
    margin-left: -62px;
    display: inline-block;
    font-size: 18px;
    color: white;
    text-align: center;
    width: 120px;
    height: 40px;
    line-height: 40px;
    border: 2px solid white;
    overflow: hidden;
    text-transform: uppercase;
    cursor: pointer;
    font-family: Arial, Verdana, sans-serif;
    transition: width .5s ease-in-out,
                margin .5s ease-in-out,
                border-radius .25s ease-in-out,
                color .25s ease-in-out;
}

.downloadbttn:hover{
    width: 40px;
    margin-left: -22px;
    border-radius: 40px;
    color: rgba(255,255,255,0);
}

.downloadbttn:hover::before{
    animation: lineDown 1s cubic-bezier(0.0,0.6,1.0,0.4) infinite .5s;
}
.downloadbttn:hover::after{
    animation: tipDown 1s cubic-bezier(0.0,0.6,1.0,0.4) infinite .5s;
}

.downloadbttn::before {
    position: absolute;
    top: 50%;
    left: 50%;
    content: '';
    background-color: white;
    margin-top: 10px;
    margin-left: -2px;
    width: 4px;
    height: 30px;
    transform: translateY(-90px);
}

.downloadbttn::after {
    position: absolute;
    top: 50%;
    left: 50%;
    content: '';
    width: 15px;
    height: 15px;
    color: white;
    border-top: solid white;
    border-left: solid white;
    margin-top: 22px;
    margin-left: -9px;
    transform: translateY(-90px) rotateZ(-135deg);
}

@keyframes tipDown {
    0%   { transform: translateY(-90px) rotateZ(-135deg); }
    100%   { transform: translateY(50px) rotateZ(-135deg); }
}
  
@keyframes lineDown {
    0%   { transform: translateY(-90px); }
    100%   { transform: translateY(50px); }
}